Magnetic alloy



Patented Sept. 17, 1929 UNITED STATES PATENT OFFICE F BENCHAMS, AND HENRY JOSEPH GARNETT, OF

DEN, 01 SUN N YSIDE, ENGLAND MAGNETIC ALLOY No Drawing. Application filed May 3, 1928, Serla This invention relates to magnetic alloys which while their magnetic properties in small fields are comparable to the best iron and their electrical resistance many times 5 greater than iron, can readily be powdered by crushing at ordinary temperatures. Such alloys moreover when heated to temperatures between 800 and 1,000 C. can be worked much as can ordinary iron while in powder form they are of particular importance in electrical and magnetic circuits and for the manufacture of cores, usually termed dust type cores of certain known telephone apparatus and which are usually formed of powdered iron obtained by grinding an electrically deposited metal.

According to this invention alloys contain:-chromium 1-10%, silicon 110% and iron the remainder but preferably not above 95%. The silicon content should be in excess of the chromium content in order to assure that the alloys are brittle at room temperature. The proportion of the silicon content varies with the degree of brittleness required, and, according to a further feature of the invention, the silicon content is from three to five times that of the chromium content, which is from 1% to 3%,

the iron content being from 85% to 95%.

A deoxidizer may be added in the proportion of 0.1 to 0.3% and preferably for this purpose we employ aluminium as the presence of manganese is undesirable. Oar- .bon may also be present up to 0.05% although its presence is not desired.

The following examples illustrate the composition and properties of alloys according to this invention: 7

Example 1 silicon, 2%

1 No. 274,960, and in. Great Britain May 18, 1927.

ability. In this form it gave a constant permeability of 75 in fields between .01 and 2 gauss.

Emample 2 An alloy containing 5% silicon, 1% chromium and the balance iron was found to have almost similar magnetic properties but its electrical resistance was only 72 microhms per centimetre cube. 80

Alloys in accordance with this invention may be made up in powder or rod form and to develop their optimum magnetic properties should be annealed at a temperature between 700 C. and 1100 C. and slowly 66 cooled.

What we claim is 1. A magnetic alloy of iron, chromium and silicon comprising' silicon 1.10%, chromium 1-10%, carbon not more than 70 05%, and iron the remainder.

2. A magnetic alloy as claimed in claim 1 in which the silicon is in excess of the chromium content.

3. A magnetic alloy of iron, chromium 7 and silicon comprising silicon 110%, chromium 110%, carbon not more than .05%, and an iron content not in excess of 95%.

4. Amagnetic alloy of iron, chromium and silicon in which the silicon is in excess of the chromium content comprising silicon 110%, chromium 110%, carbon not more than .05% and the balance iron but not in excess of 95%.

5. A magnetic alloy of iron, chromium and silicon comprising silicon 110%, chromium 1-10%, carbon not more than .05%, and the balance iron together with a small, quantity of deoxidizer such as aluminium.

6. A magnetic alloy of iron, chromium and silicon in which the silicon is in excess of the chromium content comprising silicon 110%, chromium 1-10%, carbon not more than .05%, and the balance iron but not in excess of 95% together with a small quantity of a deoxidizer such as aluminium.

7. A magnetic alloy of iron, chromium and silicon comprising silicon 1-10%,

chromium 110 an iron content not exceeding 95%, a carbon content not in excess of 0.05% and a small quantity of a deoxidizer.

8. A magnetic alloy of iron, silicon comprising silicon 57%, 12%, carbon not more than .05%, the remainder.

9. A magnetic alloy of iron, chromium and silicon comprising silicon 7%, chromium 2%, carbon not more than .05%, and iron chromium and chromlum and lIOIl the remainder.

10. A brittle magnetic alloy of iron, chromium, and silicon substantially free from carbon comprising chromium 1% to 3%, iron to and a silicon content from three to five times that of the chromium content, the proportion varying in accordance with the degree of brittleness required.

In'testimony that We claim the foregoing as our invention We have signed our names this eighteenth dav of April, 1928.

WILLOUGHBY STATHAM SMITH. HENRY JOSEPH GARNETT. JOHN ANGEL HOLDEN. 

